Package identification is a well-known method for inventory control. By providing a way to identify a specific package, manufacturers can track the construction process of a product, shippers can track a package from one location to another, and vendors can track the location of products. Bar codes are one established method for identifying products and the containers in which products are transported. Another established technology for identifying and tracking products is radio-frequency identification (RFID). RFID tags can include passive circuits in an integrated circuit (IC) that respond to a radio signal with stored identification or other data. The radio signal is provided by a “reader” (or “interrogator”) that commands the tag to transmit its stored data. U.S. Patent Publication No. 2008/0204238 describes a variety of RFID-enabled devices. In this publication, the term “downlink” refers to communications from a reader to an RFID tag. The term “uplink” refers to communications from a tag to a reader.
RFID devices are also used for monitoring purposes, e.g., as disclosed in U.S. Pat. No. 7,268,680. This patent describes a tag unit having a transmitting unit coupled to wearable electronic banding material. An RFID unit with a writeable memory is coupled to the transmitting unit. The band can include one or more conductors (which can be an antenna) that complete an electronic circuit. A layer of the band can include the RFID tag IC. The RFID tag can be read to determine that it is operational. The tag can also return data indicating whether the band is still connected to the tag IC.
Capacitively coupled RFID readers, for example as described in U.S. Pat. No. 6,236,316, electrically communicate with an identification tag to receive a unique digital code containing data relating to an object to which the identification tag is secured. The identification tag contains a transponder circuit that contains the unique digital code. The transponder circuits are typically constructed from integrated circuits and can be expensive for the intended tracking purpose. Moreover, the unique digital code is programmed into an IC on the tag in a silicon wafer fab, e.g., by laser-trimming each IC die before it is encapsulated. Since wafer processes are designed to produce large numbers of identical ICs, uniqueness requires a significant investment in programming equipment and in workflow equipment and processes to manage the ICs and guarantee uniqueness of the IDs.
U.S. Pat. No. 7,533,361 discloses a system and process for combining printable electronics with traditional electronic devices. Pre-provided electronic circuits on a substrate are electrically connected by an ink solution that includes conductive particles (e.g., silver particles). The conductive particles are used to form conductors that interconnect conventional integrated circuits and to print electronic devices with electronic functions on a conventional circuit board.
Integrated circuits are relatively expensive and this limits their application, particularly at an item level (rather than a box or pallet of products containing many items). Furthermore, equipment for programming the RFID tags is generally short-range, so a reader needs to be purchased and installed at any location where RFID communications may be required. It is also problematic to associate RFID tags with specific containers, for example by affixing the tag to the container, without error or confusion. Moreover, affixed tags can be removed and lose their effectiveness at reducing error or theft.
There is a need, therefore, for an information-storing device that provides reduced process costs and parts costs, improved security and reliability, and a simplified process flow.